1. Field of the Invention
The present invention relates to a data reproducing apparatus for recording/reproducing a digital signal such as digital broadcast data.
2. Related Background Art
With the advent of digital images and voices, rules of digital transmission are under progress even in broadcast systems. As current specifications of digital moving images, CCITT (presently ITU-T) has proposed H.261 for picture phones and TV conferences and MPEG (Moving Picture Experts Group) for CD-ROMs, and ISO/IEX and ITU-T have proposed MPEG2 for high definition transmission inclusive of HDTV. The ATV (Advanced Television) system for the next generation TV system studied in U.S.A. has been determined as a subset of MPEG2. In the ATV system, audio and video data is transmitted in the form of a transport stream as a payload of the transport packet of 188 bytes. The transport stream is constituted by continuous transport packets, and the start field of each packet is added with header information called a transport header. It is possible to identify from this header information whether data in the packet is video, audio, channel, program number, or other attribute data.
In decoding an ATV signal, a decoder unit receives (i) a transport stream on a channel selected by a user and (ii) a control signal including the selected channel and program number, and then decodes the transport stream in accordance with the control signal and outputs audio and video signals.
If a user wants to see and hear an ATV broadcast in real time, the user""s setting is reflected by the control signal supplied to the decoder unit. However, if a signal reproduced by a VTR is to be decoded, the VTR supplies only the bit stream to the decoder unit and does not supply the control signal including a program number. If the bit stream has only one program number, the decoder unit may detect it. However, if another program starts after one program is completed, images may be disturbed at the transition period between programs. The decoder unit is therefore required to always monitor program numbers. In addition, if a plurality of program numbers are recorded in a bit stream, selection means for selecting a program number becomes necessary.
The invention has been made in order to solve the above problems. It is an object of the present invention to provide a data reproducing apparatus capable of supplying a bit stream and a control signal including attributes of data such as a program number when a signal from a VTR is decoded.
It is another object of the present invention to provide a data reproducing apparatus capable of determining a priority order of a plurality of program numbers recorded in a bit stream to be sent to a decoder unit.
In an embodiment of the invention, a data reproducing apparatus for recording/reproducing a multiplexed bit stream, comprises detection means for detecting information regarding attribute data from the bit stream during reproduction and output means for outputting the detected information regarding the attribute data and the bit stream.
In another embodiment of the invention, the detection means of the data reproducing apparatus has selective output means for selecting and outputting one of a plurality set of information regarding the attribute data.
In the embodiment, information regarding the attribute data such as a program number is detected from the reproduced bit stream and outputted together with the bit stream. Accordingly, the bit stream can be decoded by using the information regarding the attribute data so that a correct reproduced signal can be always obtained even if there is a transition period between programs.
In the other embodiment, even if there is a plurality set information regarding the attribute of data, a correct reproduced signal can be always obtained.
Other objects and advantages of the invention will become apparent when read in conjunction with the accompanying drawings.